Conventionally, as a means of increasing the memory capacity of an IC (integrated circuit), memory chips are attached to a printed circuit board and this single printed circuit board is mounted on a mother board. When intending to increase the memory capacity furthermore, the method of mounting other printed circuit boards on the printed circuit board is conceivable. For example, as shown in FIG. 24, two lines of connectors 1a and 1b are provided on the bottom face of a printed circuit board 1 corresponding to two lines of connectors 5a and 5b arranged spaced from each other on a mother board 5. Connectors 1c and 1d are provided on the top face of the board 1 so as not to overlap the connectors 1a and 1b. The terminals of the connectors 1a and 1c and the terminals of the connectors 1b and 1d are connected in a corresponding relationship. A printed circuit board 2 is composed in the same size and shape as the printed circuit board 1. In order to stack the above printed circuit boards 1 and 2, the printed circuit board 1 is mounted on the mother board 5 by connecting the connectors 1a and 1b of the board 1 to the connectors 5a and 5b of the board 5, respectively. The printed circuit board 2 is mounted on the board 1 by connecting the connectors 2a and 2b provided on the bottom face of the board 2 to the connectors 1c and 1d, respectively. A repetition of such construction enables increase of the memory capacity.
However, in the case where the above printed circuit boards 1 and 2 have been mounted on the mother board 5, an additional space "t" shown in FIG. 24 is required on the mother board 5 in comparison with the case where only the printed circuit board 1 has been mounted, so that it is impossible to mount parts in high density on the mother board 5.
Another method is to separately arrange a signal terminal (not shown) for selecting a printed circuit board in the mother board and supply each selecting signal of the printed circuit boards to the corresponding printed circuit board from the signal terminal. When this method is employed, all the circuit boards can be formed in the same specification by wiring separately by cables. This, however, is unpreferable because the reliability of the connectors and the cables comes into question. When providing a passing route of the selecting signal on the lower printed circuit board, terminals of the connector which connects to the signal terminal for selecting the circuit board are located in different positions on the upper and lower circuit boards, so that it is impossible to make all the printed circuit boards the same specification.
Furthermore, there is a method of deriving a selecting signal from address signals of memories on the printed circuit boards. When using this, all wiring around the connectors becomes completely the same and no selecting signal need be supplied from the mother board. However, the circuit composition to derive the selecting signal differs. By providing the printed circuit board with a selector switch or taking other measures, the circuit pattern may be made uniform. However, this is not preferable because the reliability of the switch comes into question and the possibility of setting error arises.
Consequently, it is difficult to mount the above printed circuit boards in high density and it is necessary to produce each layer of the printed circuit boards with separate specifications, so that there is a problem that printed circuit boards are unsuited for mass production and costs rise.
This invention resolves the above problem. It has as its object the provision of a method of stacking printed circuit boards, in which the stacked printed circuit boards are composable in the same specification in terminal arrangement and wiring pattern so as to be suitable for mass production. This invention has as another object the provision of a method of stacking printed circuit boards, in which high density mounting is possible without increasing the projection area on the mother board even when many boards are stacked.
This invention has as still another object the provision of a method of stacking printed circuit boards, in which the printed circuit boards can be mounted strongly and with high reliability board on the mother board.